Social media sharing web sites and the like typically allow users to annotate media instances with tags, which may facilitate media search and organization. Recent years have witnessed an explosion of community-contributed media content available online (e.g., Flickr, Youtube, and Zooomr). Such social media repositories typically allow users to upload personal media and annotate such with descriptive keywords called tags. Given such tags, users can more conveniently organize and access shared media content. However, the tags associated with a media instance are generally in a random order and without any importance or relevance information, which limits the effectiveness of these tags in search and other operations.